From: "Paulo J. Matos" <pocmatos@gmail.com>
To: gcc@gcc.gnu.org
Subject: Re: splitting add instructions
Date: Tue, 19 Jul 2011 15:21:00 -0000 [thread overview]
Message-ID: <j046lt$sg$1@dough.gmane.org> (raw)
In-Reply-To: <201107191506.p6JF68Za016341@greed.delorie.com>
On 19/07/11 16:06, DJ Delorie wrote:
>> What's the point of the second define insn? The first insn seems to
>> take us from expansion to asm generation so I can't see where the
>> second one will come into play except in an expansion after reload
>> but that doesn't happen, right?
>
> IIRC it has to do with optimizing away compare instructions. Which
> pattern you need depends on whether the flags will get used by a
> conditional branch or not.
>
So, this seems to have to do with the post-reload comparison
optimization pass Richard mentioned. But I am still confused as to how
GCC matches them. Is *_flags any special name GCC loops for (doubtful)?
--
PMatos
next prev parent reply other threads:[~2011-07-19 15:09 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-18 16:49 Paulo J. Matos
2011-07-18 16:59 ` Richard Henderson
2011-07-18 17:31 ` Paul Koning
2011-07-18 21:20 ` Richard Henderson
2011-07-19 8:27 ` Paulo J. Matos
2011-07-19 10:21 ` Paulo J. Matos
2011-07-19 15:42 ` Richard Henderson
2011-07-19 15:58 ` Paulo J. Matos
2011-07-19 16:08 ` Paulo J. Matos
2011-07-19 16:43 ` Richard Henderson
2011-07-19 12:57 ` Paul Koning
2011-07-19 8:30 ` Paulo J. Matos
2011-07-19 10:30 ` Paulo J. Matos
2011-07-19 10:52 ` Paulo J. Matos
2011-07-19 15:06 ` Paulo J. Matos
2011-07-19 15:09 ` DJ Delorie
2011-07-19 15:21 ` Paulo J. Matos [this message]
2011-07-19 15:42 ` Richard Henderson
2011-07-19 15:42 ` Paulo J. Matos
2011-07-18 17:29 ` Ian Lance Taylor
2011-07-19 8:49 ` Paulo J. Matos
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